There are provided an inductive load current control circuit for detecting and controlling a current flowing to an inductive load with high accuracy, and a power supply.The inductive load current control circuit includes first and second switch elements connected in series between an input voltage and a ground potential, an inductive load connected to a connection point between the first and second switch elements, a third switch element having one terminal connected to the connection point between the first and second switch elements, a current comparator connected to another terminal of the third switch element to compare an output current of the third switch element with a reference current, decide and output a magnitude relation, and a switch element control circuit that controls transition from a state in which the second switch element is turned on to a state in which the first switch element is turned on according to an output of the current comparator.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An inductive load current control circuit comprising: an input terminal that inputs an input voltage; an output terminal that outputs an output voltage; a reference power source that is a current source having a current driving capability of outputting a reference current; first and second switch elements that are connected in series between the input terminal and a ground potential; an inductive load that has one terminal connected to a connection point between the first switch element and the second switch element, and another terminal connected to the output terminal to output the output voltage; a third switch element that has one terminal connected to the connection point between the first switch element and the second switch element; a current comparator that has one terminal connected to an output terminal of the reference power source and another terminal connected to another terminal of the third switch element, the current comparator comparing a current driving capability of the third switch element with a current driving capability of the reference current to decide and output a magnitude relation; and a switch element control circuit that alternately controls a first state and a second state and controls transition from the second state to the first state according to an output of the current comparator, in the first state, the first switch element being turned on and the second switch element and the third switch element being turned off to cause a current to flow from the input voltage to the inductive load, in the second state, the first switch element being turned off and the second switch element and the third switch element being turned on to cause a current to flow from the ground potential to the inductive load through the second switch element by energy accumulated in the inductive load at the first state.
2. The inductive load current control circuit according to claim 1 , wherein the reference power supply has a voltage source and a resistor that are connected in series, and provides a predetermined current from one terminal of the resistor.
3. The inductive load current control circuit according to claim 1 , wherein the reference power supply is a reference current source having a current driving capability of outputting a predetermined reference current, and the inductive load current control circuit controls an output voltage of the inductive load by controlling an amount of the current driving capability of the reference current source.
4. The inductive load current control circuit according to claim 1 , wherein the second switch element and the third switch element are transistors, and conductive resistances of the transistors are set such that a current flowing to the third transistor is smaller than a current flowing to the second transistor.
5. The inductive load current control circuit according to claim 1 , wherein the current comparator has a transistor that has one terminal connected to the reference power source, another terminal connected to the other terminal of the third switch element and a control terminal, when the control terminal being supplied with a predetermined voltage, the transistor operating such that a potential of a connection point between the other terminal of the transistor and the other terminal of the third switch element approximates to a ground potential, and the current comparator outputting a potential of an arbitrary point between the reference power source and one terminal of the transistor or a binary value of the potential as a comparison result.
6. A power supply comprising: a reference voltage generating section that outputs a reference voltage; the inductive load current control circuit according to one of claims 1 to 5 ; and an error amplifier that compares the reference voltage with the output voltage of the inductive load current control circuit to output an error voltage obtained by amplifying a difference voltage between the reference voltage and the output voltage, wherein the power supply controls a value of the reference current in the inductive load current control circuit to decrease the absolute value of the error voltage.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
March 24, 2005
September 22, 2009
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